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Biomedical subjects

F J Weber

Publications and source records attributed to F J Weber.

23 records · Page 2Linked to original sources
PubMed1979

Mechanism of action of fibrinolytic enzymes in vivo.

Plasminogen-rich and plasminogen-poor radiolabeled human fibrin clots were inserted into large veins of baboons and stump-tailed monkeys. The thrombolytic effects of plasminogen activators (urokinase, streptokinase), and plasmin preparations with activator activity (streptokinase-activated human plasmin) and without activator activity (trypsin-activated porcine plasmin, Lysofibrin) were studied. Plasminogen-free and plasminogen-rich clots lysed at equal rates. Preparations with and without activator activity were equally effective as thrombolytic agents. Endogenous activation of plasminogen in the clot thus appears not to be the essential mechanism of thrombolysis. The exogenous pathway of enzyme adsorption to fibrin fibers seems to represent an important thrombolytic mechanism. Clot lysis was achieved with doses of fibrinolytic enzymes which produced little or no significant hematologic changes including hypofibrinogenemia and decreases of other blood coagulation factor levels.

Animals↗
PubMed1979

The effect of tumor localizing porphyrins on the conversion of fibrinogen to fibrin.

The interaction of hematoporphyrin IX and two synthetic porphyrin tumor localizers, meso-tetra (4-carboxyphenyl) porphine (TCPP) and mesotetra (4-sulfonatophenyl) porphine (TPPS4) with fibrinogen was investigated in the presence and absence of light. Both TPPS4 and TCPP were found to bind to fibrinogen in greater than a 1/1 mole ratio in the absence of light. Chromatographic analysis indicated that during illumination TPP4 bound to fibrinogen to a greater extent that did either TCPP or hematoporphyrin. Both TCPP and TPPS4 were found to exhibit a greater inhibitory effect on clotting in the presence of light than did hematoporphyrin. In the absence of light and added Ca2+, both TCPP and TPPS4 were found to stimulate clotting at very specific porphyrin/fibrinogen concentration ratios, with TPPS4 being the more potent stimulator of the two. Hematoporphyrin exhibited little or no effect on clotting times. Fibrinogen, photoirradiated in the presence of the porphyrins was found to inhibit the clotting of unirradiated fibrinogen. A comparison of the stimulatory effects on clotting times by either calcium or TCPP and TPPS4 indicated that the porphyrins were capable of eliciting a greater stimulatory response than did calcium. The magnitude of the stimulatory response caused by the porphyrins alone was substantially reduced in the presence of calcium although the overall stimulatory response was increased but not additive. This suggests some interaction between either the calcium and porphyrin molecules or similarities in the respective stimulatory mechanism(s) involved. A possible correlation between these observations and the porphyrins ability to localize in tumors is also discussed.

Blood Coagulation↗
PubMed1976

Study of platelet aggregation in vivo i. Effect of bencyclan.

A 20mu diameter pore size screen was inserted into an arterio-venous bypass system in heparinized stumptailed monkeys. ADP and serotonin injection resulted in aggregation of platelets on the screen and consecutive increase in pre-screen pressure and decrease in post-screen pressure. From these changes an "aggregation index" was calculated. Bencyclan in doses of 0.5-15 mg/kg inhibited platelet aggregation in vivo. Doses of 20 mg/kg or above showed some hemolytic effect, no other undesirable effects were seen.

Adenosine Diphosphate↗